Filters can be deployed in channels or vessels in patient's bodies in a variety of medical procedures or in treating certain conditions. For example, rotating burrs are used in removing atheroma from the lumen of patients' blood vessels. These burrs can effectively dislodge the atheroma, but the dislodged material will simply float downstream with the flow of blood through the vessel. Filters can be used to capture such dislodged material before it is allowed to drift too far downstream, possibly occluding blood flow through a more narrow vessel.
Some researchers have proposed various traps or filters for capturing the particulate matter released or created in such procedures. However, most such filters generally have not proven to be exceptionally effective in actual use. These filters tend to be cumbersome to use and accurate deployment is problematic because if they are not properly seated in the vessel they can drift to a more distal site where they are likely to do more harm than good. In addition, these filters are generally capable of only trapping relatively large thrombi and are not effective for removing smaller embolic particles from the blood stream.
The problems with most temporary filters, which are intended to be used only during a particular procedure then retracted with the thrombi trapped therein, are more pronounced. Even if the trap does effectively capture the dislodged material, it has proven to be relatively difficult or complex to retract the trap back into the catheter through which it was delivered without simply dumping the trapped thrombi back into the blood stream, defeating the purpose of the temporary filter device. For this reason, most atherectomy devices and the like tend to aspirate the patient's blood during the procedure to remove the dislodged material entrained therein.
One promising filter design which overcomes many of these difficulties is shown in international Publication No. WO 96/01591 (the publication of PCT International Application No. PCT/US95/08613), the teachings of which are incorporated herein by reference. Generally, this reference teaches a trap which can be used to filter particles from blood or other fluid moving through a body vessel. In one illustrated embodiment, this trap includes a basket 270 which can be deployed and retracted through a catheter or the like, making it particularly suitable for use in minimally invasive procedures such as angioplasty or atherectomy procedures. The fact that this trap is optimally carried on a mandrel 260 further enhances its utility as most common angioplasty balloons and atherectomy devices are used in conjunction with such mandrels. While this trap is very useful and shows great promise in many common procedures, it may be possible to improve the ease with which it may be deployed and/or retracted.
Some medical devices are also permanently deployed in a patient's vessel, but properly positioning these devices at the desired treatment site using minimally invasive techniques can be cumbersome. For example, occlusion devices can be used to occlude an arterial vessel or a septal defect. Some of these occlusion devices may radially expand into an enlarged configuration wherein they substantially fill the lumen of the vessel or extend over the margins on either side of a septal defect. When deploying these occlusion devices through a delivery catheter, though, the friction between the occlusion device and the wall of the catheter can make it difficult to deploy the device at a precisely selected location. These problems are even more pronounced in longer catheters tracking through more tortuous paths.